In recent years, development of a swallowable capsule endoscope is underway in the field of endoscopes. This capsule endoscope includes an imaging function and a radio function. The capsule endoscope functions to move in patient's organs, e.g., the esophagus, the stomach and the small intestine according to peristaltic movements of the organs and to sequentially pick up in-vivo images after it is swallowed from a patient's mouth for observation of the interior of a body cavity until being naturally discharged (see, for example, Patent Document 1).
During the movement of the capsule endoscope in the body cavities, image data picked up in the body cavities by the capsule endoscope is sequentially transmitted to the outside of the patient's body by radio communication and accumulated in a memory provided in a receiver outside of the patient's body. A doctor or a nurse can diagnose the patient based on images displayed on a display based on the image data accumulated in the memory.    Patent Document 1: Japanese Patent Application Laid-Open No. 2003-19111    Patent Document 2: Specification of US Patent Application Publication No. 2002/109774